This research is designed to evaluate age related changes in central and autonomic nervous system activation in response to infusion of catecholamines. The focus is upon age and sex differences in autonomic end-organ response to epinephrine and norepinephrine infusion at low moderate dosage levels and on quantitative relationships among end-organ activities (ANS), CNS, and endocrine activity. A biological model of activation is proposed and developed as a parallel to psychological studies of age-related performance decrements where psychological stressors are employed (i.e., paced:p erformance and learning tasks).